Alcohol use, particularly among those in the criminal justice system, imposes tremendous costs on individuals and society. In traditional community supervision models, sanctions for violations-if applied at all-often occur only after fairly seriou offenses and may not be imposed until weeks or months after the precipitating offense. However, a growing body of evidence suggests that punishment certainty and celerity create a stronger deterrent to illegal activity than punishment severity. South Dakota's 24/7 Sobriety Project (hereafter, 24/7) applied this concept of swift and certain sanctions for alcohol violation initially to repeat drunk driving offenders and eventually to other alcohol-involved offenders. The program requires participants to submit to breathalyzer tests twice per day or to wear continuous alcohol monitoring bracelets. Those testing positive or missing a test face an immediate, but brief, jail term (typically a night or two). More than 25,000 South Dakotans have participated in 24/7 since 2005. RAND's NIAAA-funded evaluation provides evidence that the program reduced county-level arrests for repeat drunk driving by 12%, arrests for domestic violence by 9%, and crashes among males aged 18-40 by 4% (Kilmer et al., 2013). Even though 24/7 was recently added to the list of impaired driving countermeasures eligible for federal traffic safety funds (MAP-21), rigorous scientific evidence is still needed to ascertain how well the program works outside of South Dakota. This R21 starts with an evaluation of its replication in a state-North Dakota-that is similar to South Dakota in terms of the geography, density and magnitude of its alcohol problem, but where post- implementation data on DUI arrests and motor vehicle fatalities call into question the effectiveness of 24/7. Our central hypothesis is that, if the program is successfully replicated, rates of public harms arising from alcohol misuse, such as alcohol-related traffic accidents, DUI, and alcohol-related violence, would be significantly lower than without the program as we found in South Dakota. Our unprecedented access to data and stakeholders combined with quasi- experimental methods provide a unique opportunity to examine this important issue (ND's Attorney General has already made data available to RAND and supports our independent evaluation of their 24/7 program). The extent to which South Dakota's program can be successfully replicated in another state will provide timely information about whether this program can serve as a national alcohol control model.